Joe Donnelly of Indiana on Saturday became the second Democratic senator to back Donald Trump’s pick to run the CIA, Gina Haspel, whose nomination is in question over her role in a rendition and torture programme run by the agency after 9/11.

In a statement issued on Saturday, Donnelly said he made his decision after a “tough, frank and extensive discussion” with Haspel, the acting CIA director, on topics including “issues of detention and interrogation”.

“I believe she has learned from the past,” he said, also citing the “strong support of both her colleagues at the agency and former CIA directors [Michael] Hayden, [Leon] Panetta and [John] Brennan, who served under Presidents Bush and Obama”.

Donnelly is up for re-election in a state Trump won handily in 2016. The president attacked the senator this week, at a campaign-style rally in Elkhart, calling him “Sleeping Joe” and criticising his record in Washington, which Trump said made Donnelly, who was elected in 2012, an “incredible swamp person”.

The rally came two days after a fiercely contested Republican primary, which was won in an upset by Mike Braun, a wealthy businessman and former state lawmaker.

The other Democrat to support Haspel is Joe Manchin of West Virginia, another senator up for re-election in a red state. His opponent will be the state attorney general, Patrick Morrisey, who this week came through a Republican primary featuring the ex-coal boss and convicted felon Don Blankenship, whom Trump rejected as unelectable. Manchin called Haspel “a person of great character”.

Two Republican senators have announced their opposition to Haspel’s nomination: Rand Paul of Kentucky and John McCain of Arizona, who is battling brain cancer and is not expected to be present for the voting.

Supporters of Haspel are pushing for votes by the Senate intelligence committee and the full Senate before the Memorial Day break, at the end of the month. Republicans hold a 51-49 majority and have Vice-President Mike Pence to break any tie.

Haspel appeared before the committee on Wednesday, in a hearing that was interrupted by protesters. She faced sharp questioning from Democrats over her role in the agency’s use of “enhanced interrogation techniques”, commonly referred to as torture, on terrorist suspects.

Presented with Trump’s stated support for such techniques, Haspel said she did not “believe that torture works”. Asked if she would carry out a presidential order to use techniques including waterboarding, she said: “I would not restart under any circumstances an interrogation program at CIA, under any circumstances.”

Repeatedly asked by the California senator Kamala Harris for a yes or no answer on whether torture was immoral, she declined to say either way. McCain subsequently issued a statement in which he said Haspel’s refusal to condemn torture as immoral was “disqualifying”.

Dick Cheney, vice-president to George W Bush, told Fox News on Friday he thought “the techniques we used were not torture. A lot of people try to call it that, but it wasn’t deemed torture at the time. People want to go back and try to rewrite history, but if it were my call, I’d do it again.”

Haspel is a career CIA officer who has spent much of her time at the agency working under cover. Cheney said: “The people I know at the agency are very enthusiastic about having one of their own, so to speak, in the driver’s seat at the CIA.”

The American Civil Liberties Union said the Senate “should not even agree to vote on this nomination until it gets full information and honesty from this nominee”.

Trump’s nomination of the White House doctor Ronny Jackson to run the Department of Veterans Affairs collapsed last month, in the face of allegations collected by the Montana Democrat Jon Tester, whom Trump subsequently attacked.

The president has vociferously supported Haspel, for being “tough on terror”. After Wednesday’s hearing, he tweeted that Haspel “did a spectacular job today”.